Today’s space vehicles use rocket fuel to launch them out of Earth’s atmosphere and then solar power takes over to keep them in orbit—something the world takes for granted. But did you know that the concept of using solar power for satellites came about because of a three-and-a-half pound hunk of parts that the United States launched into orbit 57 years ago? That satellite, called Vanguard 1, set the standard for the solar power technology we use in today’s spacecraft.

In 1958, the U.S.-Soviet Union space race was heating up. The Soviets had already launched the world’s first Earth orbital satellites (Sputnik-1 and Sputnik-2) in 1957; the U.S. was lagging behind and didn’t put up its first satellite (Explorer 1) until January 1958. Then came Vanguard 1.

Blasting off from Cape Canaveral, Fla., on March 17, 1958, Vanguard 1 was a small earth-orbiting satellite designed to test the capabilities of a three-stage launch vehicle and the effects of the environment on a satellite and its systems in Earth orbit. It also was used to obtain geodetic measurements through orbit analysis. More important—it was the first satellite to be powered by solar energy.

Referred to derisively by Soviet Premier Nikita Khrushchev as “the grapefruit satellite,” the 6.4-inch, 3.5-pound Vanguard 1 nevertheless achieved the highest altitude of any man-made vehicle to that point. It was powered by six photovoltaic solar cells that produced less than one megawatt of energy. The last signals from Vanguard 1 were recorded in Quito, Ecuador, in May 1964, but Vanguard 1 continues to orbit the Earth today and is tracked optically. It is the oldest man-made satellite and is expected to remain in orbit well into the 22nd century, according to the U. S. Naval Research Laboratory (NRL).

In the months after Vanguard 1 was put into space, Explorer II, Vanguard II and Sputnik-3 were launched with PV-powered systems on board. And while efforts to commercialize the silicon solar cell failed in the 1950s and 1960s, PV technology was used successfully in powering satellites and remains the accepted energy source for space applications today.

In 2008, the NRL celebrated Vanguard 1’s 50th anniversary with a five-minute video that included actual launch footage from 1958. Talk about a throwback!